Variable curve electrophysiology catheter

ABSTRACT

An electrode tip assembly attachable to the end of a catheter for supporting a tip electrode for percutaneous insertion into a living body having a steering mechanism includes an elongated body bendable in response to external forces to steer the tip electrode. The body is connected at its distal end to the tip electrode. At least one steering wire is attached to the elongated body for transmitting bending force to the body from a remote control mechanism. An movable stiffening member, preferably in the form of a sleeve or rod provides a variable fulcrum for bending of the body in response to an applied bending force. A control stylet or sleeve extends through the catheter and is attached to the stiffening member for moving the stiffening member in a distal/proximal direction or for rotating it relative to the body.

FIELD OF THE INVENTION

This invention relates to catheters that can by steered by externalcontrols.

BACKGROUND OF THE INVENTION

Cardiac mapping is used to locate aberrant electrical pathways andcurrents emanating within the heart. Such aberrant pathways causeirregular contractions of the heart muscle resulting in life-threateningpatterns or disrhythmias.

Intercardiac mapping requires careful positioning of the electrodeswithin the heart. Various steering mechanisms for catheters carryingsuch electrodes have heretofore been developed and used.

To provide catheters having different curve configurations to accessvarious endocardial sites, physicians have to stock and use number ofdifferent catheters, each of which provides a different curveconfiguration. Commercially available catheters, thus, come in sets,which often provide 4 to 7 different curve configurations by usingdifferent catheters.

This approach presents serious disadvantages, because the physicianoften must repeatedly remove and re-insert these different catheters tocomplete a procedure on a given patient.

A need exists for a catheter which could be steered into differentcurvatures without removing and re-inserting a different catheter.

SUMMARY OF THE INVENTION

The present invention provides a catheter, usable in both diagnostic andtherapeutic applications, that enables a physician to swiftly andaccurately change the configuration of the distal curve of the catheteras it is steered within the body of a patient. The catheter thatembodies the invention allows physicians to access many more endocardiumsites than heretofore achievable by a single catheter. In its broadestaspect, the invention provides a catheter which enables a physician toalter the physical characteristics of a catheter inserted within aliving body by manipulation of external controls.

One aspect of the invention provides a catheter having an internalfulcrum that can be moved within the catheter to different distancesrelative to the distal tip by external manipulation. Movement of theinternal fulcrum results in creating different curvature radii forbending of the distal tip.

The internal fulcrum that the invention provides is usable in connectionwith unidirectional catheters, as well as bi-directional, steerablecatheters.

The invention provides a catheter in which a longer fulcrum-to-distaltip distance can be provided for accessing and measuring electricalactivity in portions of the heart such as the coronary sinus, the rightventricular overflow tract and the HIS bundle. Similarly, a shorterfulcrum-to-tip distance can be used to access such areas as the highright atrium and the right and left ventricle apex of the heart.

An important advantage of the present invention is to provide a catheterwhich enables the physician to reduce the time required for a procedureby changing the type of curvature obtainable by the catheter while thecatheter is still in the patient's body. A yet further aspect of theinvention is to provide a catheter steering mechanism wherein a variablefulcrum is provided but wherein currently available steering componentsand mechanisms can be utilized.

In accordance with a still further aspect of the invention, a movablefulcrum within a catheter is provided by utilizing a stylet that can beproximally-distally manipulated and which is connected to an annulartube, the distal end of which forms a fulcrum within a catheter. Afurther related aspect is the ability to use such moveable tubes ofdifferent materials, having different rigidity characteristics. In thisregard, a relatively rigid material can be used to provide an abrupt orshort radius distal curvature of the catheter and a more pliable tubecould be used, if desired, to produce a curve with more gradualcharacteristics or a larger radius. In accordance with still furtheraspects of the invention, it is possible to substitute a differentslidable stiffening mechanism within the catheter, for example, asegment of a movable interior stiffening rod can be employed rather thanan annular tube. In accordance with yet another embodiment of theinvention the stiffening member is provided with a distal end havingcircumferential segments terminating at different distal positionsrelative to the steering body, thus enabling the changing of fulcrumpoints for bending of the steering body by rotating the stiffeningmember relative to the steering body. In this embodiment the stiffeningmember may be carried on the distal end of a rotatable sleeve positionedin the catheter.

Briefly summarized, the invention provides a catheter for percutaneousinsertion into a living body having a steering mechanism that includesan elongated body bendable in response to external forces to steer thecatheter tip. The body has a proximal end for attachment to a guide tubelocated within the body of the catheter and a distal end for carrying anoperative element such as a tip electrode. At least one steering wire isattached to the elongated body for transmitting bending force to thebody from a remote control mechanism. An axially movable stiffeningmember, preferably in the form of an axially or rotationally movablesleeve or rod provides a variable fulcrum for bending of the body inresponse to an applied bending force. A control stylet or wire extendsthrough the length of the catheter body and is attached to thestiffening member for moving the stiffening member in a distal/proximaldirection.

Further, objects and advantages of the invention will become apparentfrom the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of a catheter and catheter handle assembly inaccordance with the invention with some interior parts shown by means ofphantom lines;

FIG. 2 is a view of the catheter shown in FIG. 1 with the tip portionbroken away and shown in cross-section on a greatly enlarged scale andshowing a moveable sleeve in a proximal position;

FIG. 3 is a view in accordance with FIG. 2 showing the sleeve in a moredistal position;

FIG. 4 is a top sectional view of the handle of the device of thepresent invention on a greatly enlarged scale;

FIG. 5 is a sectional view of a tip portion of a catheter in accordancewith another embodiment of the invention;

FIG. 6 is a view of the device of FIG. 5 with the curve adjustingmandrel advanced to a more distal position;

FIG. 7 is a view of a catheter showing an alternate embodiment of theinvention utilizing a rotatable sleeve;

FIG. 8 is a perspective view showing the configuration of the distal endof the sleeve of the device shown in FIG. 7;

FIG. 9 is a fragmentary cross-sectional view showing the controlmechanism in the distal portion of the handle of the handle of thecatheter of FIG. 7;

FIG. 10 is a view of a catheter showing bendable axially movablestiffening member in a retracted approximal position, and;

FIG. 11 is a sectional view of the distal tip portion of the catheter ofFIG. 10 with the stiffening member advanced to its most distal position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a steerable catheter 10 that embodies the features of theinvention. The catheter 10 includes several main parts: a handle 12, acatheter tube or body 14, and a steerable distal tip assembly 16. Inuse, the catheter 10 provides electrophysiology diagnosis or therapy inthe interior regions of the heart.

When used for this purpose, a physician grips the handle 12 andmaneuvers the catheter body 14 through a main vein or artery (which istypically the femoral vein) into the interior region of the heart thatis to be treated. The physician then further steers the distal tipassembly 16 to place it in contact with the tissue that is to beablated. The physician directs energy to an electrode in the assembly 16to ablate the tissue contacted.

As FIG. 4 shows, the handle 12 encloses a steering mechanism which maybe in the form of a rotating cam wheel of the type shown in U.S. Pat.No. 5,195,968. While one form of steering mechanism 18 is shown forpurposes of illustration, it will be understood that many othermechanisms that allow for selective pulling of the steering wires in thecatheter can be substituted.

As FIG. 4 best shows, the handle assembly 12 includes a housing 20 thatencloses the steering mechanism 18. The steering mechanism 18 includes arotatable wheel or cam 22 carried on a shaft 24 within the housing 20.The rotatable cam 22 and control knob 26 are attached to shaft 24 bysplines. Clockwise movement of the control knob 26 rotates the cam 22clockwise pulling on wire 56. Counterclockwise movement of the controlknob 26 reverses the direction of each of these movements and results inpulling wire 58. Various other mechanisms can be substituted to applytension to wires 56 and 58 in place of that shown in FIG. 4.

The steering wires 56 and 58 exit the front of the housing 20 throughthe interior bore of a tension screw assembly 60. The distal ends of thesteering wires 56 and 58 are attached to a steering wire or spring inthe electrode tip assembly 16.

The catheter body 14 is a flexible shaft attached to the handle 12.While it can be variously constructed, in a preferred embodiment, thecatheter body 14 is a length of stainless steel coiled into a flexiblespring 25 enclosing an interior bore 27 forming a guide tube which inturn is enclosed in a braided sheath 29 of plastic material. Thesteering wires 56 and 58 preferably pass through the interior bore 27,which leads to the distal tip assembly 16 where the steering wire areattached to a bendable main support wire 34. In the illustratedembodiment, the main support wire 34 is made of stainless steel flatwire stock in an elongated shape about 0.035 inch wide and about 0.005inch thick. The main support wire 34 is about 3 inches in total length.

In the distal end of the catheter body 14 there is no surrounding sheathor shield, leaving the steering assembly exposed. Positioned in thedistal end region and overlying the distal end of coil 25 is a curveadjusting tube 61. The proximal end of curve adjusting tube 61 isattached to a mandrel 62 that extends within the catheter body 14 intohandle 12. The proximal end of mandrel 62 is connected to a slidable,bi-directional adjuster knob 64. Sliding of knob 64 enables thepractitioner to slide the adjusting tube 61 axially within the catheterbody 14 to a more proximal or more distal location as desired. The moreproximal and more distal positions of knob 64 are shown in FIG. 1 bymeans of phantom lines. In the more proximal location illustrated inFIG. 2, the curve adjusting tube 61 is positioned to permit the maximumcurvature of distal tip assembly 16 to position 16a illustrated by meansof phantom lines. In the more distal location illustrated in FIG. 3, thetube 61, which acts as a slidable fulcrum for the tip, steering of thetip by means of knob 26 causes a shorter portion of the tip 16 to curveto a sharper curve illustrated by phantom lines 16b in FIG. 3.

In the alternate embodiment illustrated in FIGS. 5 and 6, the mandrel62, which may be provided with an enlarged end section, is positionedfor axial sliding within a channel 66 in similar to that shown in FIGS.2 and 3 the distal tip 16 can be bent to different curvatures 16a or 16bas shown in FIGS. 5 and 6. It will readily be apparent that intermediatecurve shapes other than those illustrated by lines 16a and 16b can beprovided by positioning level 64 in an intermediate position.

In the preferred embodiment of the device shown in FIGS. 2 and 3 outersleeve 29 is formed of Kevlar. Mandrel 62 is formed of a 0.02 inchstainless steel wire running parallel between the guide coil 25 and theinside of Kevlar tubing 29. Wire 64 is preferably attached on theoutside of a 2.5 inch long 0.050 inch inter diameter/0.055 inch outerdiameter length of tube that forms sleeve 60. The tube can be made ofstainless steel, nitinol alloy or a polymeric material such as polyamideor other polymer. In the preferred embodiment, a polyamide tube isreinforced by a stainless steel coil embedded in the wall. To provide awell defined movable fulcrum the sleeve is formed of a rigid material.It will also be apparent that in the event the tube 61 is made from arelatively softer material or more flexible material such as apolyurethane, silicone, or polyethylene, it will provide a stiffeningeffect but have less effect on the changing of the curve radius of thetip.

In a further embodiment shown in FIGS. 7-9 a tube 160 is rotatablerelative to the steering wire 34 rather than being axially movablerelative thereto. In this case a rotatable sleeve concentric with spring25 and located within bore 27 is attached to tube 160 for the purpose ofapplying rotational forces thereto. Tube 160 is provided with a distalend having circumferential segments 162, 164, 166, and 168 of differinglengths. Each of these circumferential segments provides a fulcrum orstiffening member spaced a different distance from the distal tip of thecatheter and thus provides for as many different curvature shapes of thetip as there are segments.

Tube 160 is rotated by applying a force to control knob 170 located inhandle 12. Tube 160 is connected to control handle 170 by means of atorque transmitting tube 172. Since the control wire 34 will tend tobend the distal tip 16 from side to side in a single plane, the fulcrumlength provided by rotatable tube 160 is dependent on which of thesegments 162, 164, 166 or 168 is positioned in the plane in whichcontrol wire 34 bends. Appropriate markings on handle 12 can be providedto indicate the position in which control knob 170 is rotated. Thus, thephysician can readily change the fulcrum length or stiffnesscharacteristics of the distal tip of the catheter by manually rotatingknob 170.

In the embodiment of FIG. 10, a stiffening member 180 is shown in theform of a flexible polymeric tube. Any flexible material can be used asa material of construction for tube 180. A rod 62 of the type in FIGS. 5and 6 is used as a stiffening member. Any flexible materials such asplastic, metal or other bendable materials of construction can be used.

Referring to FIGS. 10 and 11, when sleeve 180 is in the retractedposition shown in FIG. 10, the tip 16 can be steered easily with greatlyreduced resistance to bending when bending forces are applied to the tipby means of steering mechanism 18. When the stiffening member 180 isadvanced to its most distal position shown in FIG. 11, the same cathetercan behave as one that is stiffer or resistent to bending. By placing aflexible stiffening member in an intermediate position, it is possibleto alter the curve characteristics of a catheter by stiffening a portionof the steerable tip portion but not the more distal portion thusproviding a further range of possible curve configurations obtainable bythe steerable catheter tip.

It will, thus, be appreciated that in accordance with the invention, thecharacteristics of the distal tip of a steerable catheter can be alteredby means of movement of a remote control member. This alteration canoccur when the catheter is being used within a living body. Theinvention, thus, makes possible the alteration of numerouscharacteristics of a catheter without the need for withdrawing thecatheter from the body.

What is claimed is:
 1. A catheter having a steerable distal tip assemblyincludinga body located in said distal tip assembly bendable in responseto external forces, the body having opposite end portions and beingconnected to a steering mechanism by at least one steering wire forapplying a bending force to the body, a stiffening member positioned inthe catheter movable relative to said body in response to movement of anexternal control, said stiffening member providing a fulcrum spaced adistance from the distal end of the body said distance being variable bymanipulation of said external control for varying the radius ofcurvature of the body in response to bending forces applied by saidsteering mechanism, means located within the catheter for translating aforce applied to said external control member to said stiffening memberfor causing the stiffening member to be moved in response to forcesapplied to said control member.
 2. A tip assembly according to claim1wherein the stiffening member comprises an annular solid sleeve.
 3. Atip assembly according to claim 2wherein the stiffening member comprisesa polymeric material or a metal.
 4. An assembly according to claim 1wherein said stiffening member is axially movable relative to saidbendable body.
 5. An assembly according to claim 1 wherein saidstiffening member is rotatably movable relative to said bendable body.6. A catheter includingan elongated flexible tubular catheter bodyhaving a proximal end and a distal end, an electrode tip assemblyaffixed to the distal end of said catheter body, a steering assemblylocated within the catheter body and connected to said tip assemblyincluding a guide tube having a proximal end and a distal end, and asupport wire bendable in response to external forces, the support wirehaving a proximal end attached to the guide tube distal end and a distalend that extends beyond the guide tube distal end, said steeringassembly being operatively positioned in said catheter body to causebending thereof in response to bending of said support wire, an axiallymovable stiffening member within said catheter body providing a fulcrumspaced a variable distance from the distal end of the support wire forvarying the radius of curvature of the support wire in response to anapplied bending force, and means attached to said wire for applying abending force to the wire.
 7. A catheter according to claim 6wherein thestiffening member is in the form of an annular sleeve positioned aroundthe support wire and guide tube.
 8. A catheter according to claim7wherein the stiffening member is attached to a stylet axially movablewithin said catheter body.
 9. A catheter according to claim 6wherein thestiffening member comprises metal or polymeric rod.
 10. An electrodesupport assembly according to claim 6wherein the stiffening membercomprises a metal annularly shaped tube that surrounds said guide tube.11. An electrode support assembly according to claim 10wherein thestiffening member is movable in response to motion applied to a slidablelever contained in a control handle on the proximal end of the catheter,and means are included to operatively connect said stiffening member tosaid lever.
 12. An electrode tip assembly attachable to the end of acatheter for supporting a tip electrode for percutaneous insertion intoa living body comprisingan elongated body bendable in response toexternal forces to steer the tip electrode, the body having a proximalend for attachment to the catheter and a distal end for carrying the tipelectrode and at least one steering wire attached to the body fortransmitting bending force to the body from a remote control mechanism,said control mechanism being operatively connected to said steering wireto apply forces thereto, said catheter being bendable in response tobending of said body, an axially movable stiffening member providing avariable fulcrum for bending of the body in response to an appliedbending force, and a control stylet extending through the length of thecatheter and attached to the stiffening member for moving the stiffeningmember in a distal/proximal direction.
 13. An electrode support assemblyaccording to claim 12wherein the stiffening member comprises a stiffannularly shaped metal or polymeric tube.
 14. A cardiac probe includinga distal tip assembly supporting at least one electrode for measurementof electrical activity within the heart or for ablation of cardiactissue, comprisingan elongated, flexible tubular catheter body having aproximal end and a distal end, said distal tip assembly being attachedto said distal end of said catheter body, said probe including a handleportion provided with a steering mechanism attached to the proximal endof said catheter body and a steering wire assembly connected to saidsteering mechanism and extending from said handle to said distal tipassembly for bending said assembly in response to forces applied to saidsteering mechanism, characterized in that a stiffening member iscontained in said catheter body adjacent to said distal tip assembly,said stiffening member being manipulatable by a manually moveablecontrol located in said handle said control being operatively connectedto said stiffening member and wherein manipulation of said control movessaid stiffening member relative to said steering mechanism and therebydefines a fulcrum moveable relative to said steering mechanism that,when moved, changes the length of said distal tip assembly that isdeflected when said distal tip assembly is caused to bend.